The present invention relates to an ultralight sound- and shock-absorbing component set for motor vehicles according to the precharacterising clause of claim 1 and component therefor.
Large-area vehicle parts, such as floor panels, roof panels, engine bonnet, boot lid or doors and side panels, tend, because of their low level of inherent strength, to become deformed, vibrate and oscillate during travel. This behaviour is conventionally countered by the application of damping materials, in particular heavy bituminous coatings. To reduce the transmission of travel noise to the inside of a vehicle, multi-layer sound-insulation assemblies have long been used in the automobile industry. These sound-insulation assemblies are generally designed as spring/weight systems and all comprise a heavy layer coupled with a resilient spring layer, in order to damp the vibrations suffered by the large-area bodywork parts and to restrain the passage of airborne noise.
Such a sound-insulation assembly is described, for example, in EP-0,334,178 and substantially comprises a flexible foam layer facing the bodywork part with a tendency to vibrate, which layer acts as the spring of the spring/weight system, a virtually compact, air-impermeable layer of the same material acting as the weight of the spring/weight system and a decorative or carpet layer arranged thereon. With this construction, the weight of the heavy layer may be reduced by up to 40% and the weight of the entire sound insulation system may thus also be reduced relative to the known spring/weight systems, albeit with diminished acoustic efficacy. In general, spring/weight arrangements always lead to resonant incursions in the sound insulation, which regularly lie in the range of frequencies of the same order of magnitude as the lower engine frequencies and are particularly undesirable in this range. This phenomenon thus fundamentally prevents an extremely light construction.
However, the general desire of the automobile industry is further to reduce vehicle weight and in particular the weight of internal trim. It was therefore proposed in PCT/CH 96/00381 to provide a sound-insulating component which is more than 50% lighter than conventional sound-insulation assemblies. The structure of this component differs from the above-described insulation assemblies in that the heavy layer of the conventional spring/weight systems is replaced by a light-weight, relatively thin, microporous, rigid fibre layer and particular attention is paid to the flow behaviour of the air in the boundary area between the bodywork part and the fitting assembly. Thus, the relatively heavy-weight damping mechanism of the conventional spring/weight systems is reduced fundamentally in favour of a light-weight, efficient sound-absorption capacity.
It is a further desire of the automobile industry also to equip the interior of vehicles with shock-absorbing means, to protect the passengers as far as possible from serious injuries in the event of a vehicle collision. To this end, passenger compartments are currently equipped with a shock-absorbing lining. Such linings as a rule comprise a more or less expensive carpet layer, which is backed with a shock-absorbing layer. These shock-absorbing internal linings are suitable for absorbing completely impact energy of 90 Joules and impulses of less than 400 daN. These linings also take the form of spring/weight systems and exhibit the known disadvantages thereof. Furthermore, these combined shock- and sound-absorbing linings are undesirably thick. It has therefore also already been proposed, in CH 1415/96, to provide a thin lining part with improved sound- and shock-absorbing properties. This system also behaves substantially as a spring/weight system and additionally makes use of dissipative mechanisms in the boundary area between bodywork part and insulation component.
Sound-absorbing components are also known from U.S. Pat. No. 4,479,992, which are not designed as spring/weight systems. These components comprise an alveolate structure, which is covered with at least one open-cell nonwoven. These components are relatively bulky and are easily deformed, i.e. are not suitable as shock-absorbers.
It is the object of the present invention to provide a lining component for vehicle interiors which combines the properties of conventional sound-insulation and shock-absorbers without being, as a result, heavier and bulkier than these. It is in particular the object of the present invention to provide a thin, ultralight, sound- and shock-absorbing lining component.
This is achieved according to the invention by a fitting assembly having the features of claim 1 and in particular by a multi-layer fitting assembly without heavy layer, wherein one of the layers comprises a plurality of adjacently arranged hollow articles, whose walls are substantially perpendicular to the fitting surface and laterally perforated, preferably at least partially slotted, in such a way that a cohesive labyrinth of cavities is formed thereby.
With such a labyrinth of cavities, it is possible on the one hand to improve substantially the acoustic absorption capacity or to reduce the overall thickness of the fitting assembly relative to conventional system without losing acoustic absorption capacity. On the other hand, the walls of the hollow articles arranged substantially perpendicularly to the fitting surface exhibit particularly advantageous compression behaviour. If a body impacts against the fitting assembly, these impact forces compress the walls positioned substantially in the impact direction, or these walls buckle or break.
It goes without saying that the person skilled in the art may produce the desired compression behaviour by a suitable choice and dimensioning of the material. For the present application, plateau-type compression behaviour is desirable.
In a preferred embodiment, therefore, the walls of the hollow articles are dimensioned in such a way that they permit compression of at least 50% under a maximum plateau tension of 0.5 MPa less than "PHgr" less than 1.2 MPa and convert an impact energy of approx. 0.5 MJ/m3 inelastically and completely into deformation.
In a further embodiment, this fitting assembly comprises a microporous stiffening layer, which exhibits total air flow resistance of 900 Ns/m3 less than Rt less than 2000 Ns/m3, flexural strength of 0.027 Nm less than B less than 0.275 Nm and a weight per unit area of 0.3 kg/m2 less than mF less than 0.7 kg/m2.
Such an extremely light stiffening layer is important for the acoustic efficacy of the fitting assembly. The air flow resistance has a substantial influence on the absorption behaviour of this layer and may be determined by the selection of a suitable open-cell structure (nonwoven fabric or foam). The relatively high flexural strength of this layer is significant for the low-frequency range and may contribute considerably to the fact that the entire fitting assembly is self-supporting.
Further embodiments of the component set according to the invention and the particular technical features thereof are revealed by the subclaims.
The advantages of this acoustically effective shock-absorber arrangement are directly obvious to the person skilled in the art and are to be found, in particular, in the fact that the structure lacks a heavy layer, i.e. is ultralight and thin.